Breaking overnight, a historic deal. We have a real opportunity to achieve a comprehensive deal. The international community and longtime enemy, get a late-night landmark deal to freeze iran's nuclear program, will it stop iran from getting the bomb? If it falls apart, is war next? Joining us this morning, secretary of state john kerry. We go inside iran. Plus, martha raddatz and christiane amanpour with all of the breaking details and analysis. Then, our roundtable takes on the stunning move to shake up the senate. And the last fascination with jfk. Plus, facebook founder mark zuckerberg and maya angelou, calypso queen. I'm proud of that song. Right here this sunday morning. And we begin with that big news breaking overnight, after months of secret talks and high-stakes policy, a deal between iran and the west to suspend its nuclear program and get some relief from those sanctions that have crippled iran's economy, it's sparking split reactions in washington and around the world. We'll get right to secretary of state john kerry in a moment. But first, abc's chief foreign correspondent terry moran has more on the fine print and fierce response. He's in geneva. Good morning, terry. Reporter: Good morning, george. The deal hammered out in the wee hours of the morning here is full of either promise or peril, depending on your point of view. The headline, iran has agreed to suspend the growth of its nuclear program. It will degrade some of the most dangerous uranium it has. And it's agreed to open its facilities to daily inspections by international officials. The u.S. Has agreed to ease sanctions. That's a relatively small portion of the sanctions that have brought iran's economy to its knee. This whole thing is temporary. Six months, neither side here trust each other. They enter into negotiations to try to reach a comprehensive agreement. That is a very tough nut to crack. No surprise, the israeli prime minister, benjamin netanyahu, trashing the deal, calling it a historic mistake. He's going to do everything he can to prevent from iran from getting a nuclear weapon. Reporter: Absolutely, no question about that, george, and what israel is going to try to do now is to rally its support in united states and other countries. Especially in congress to try to block this agreement by getting new sanctions imposed. Israel has made clear, the prime minister has made clear that israel is ready to go it alone, if necessary, so it will prepare, if necessary, some kind of military action, probably with the quiet task and support of saudi arabia and other countries in the region. The real test, of course, is six months from now, will this lead to a deal that actually rolls back iran's nuclear program? Reporter: Yeah, that's the big question. That's incredibly difficult negotiation going forward, and the test of whether or not all of this, people are talking about how it's making history, a test of whether it's successful, is if by the end of the day, iran can become a normal nuclear country. Can it be trusted with it? And can it join in a new kind of relationship with the united states and the west? Those are the stakes here and they are very, very high. No question about that. Terry moran, thanks very much.

This transcript has been automatically generated and may not be 100% accurate.